Determination of onset of plasticity (yielding) and comparison of local mechanical properties of friction stir welded aluminum alloys using the micro‐ and nano‐indentation techniques

Abstract

PurposeThe purpose of this paper is to determine if the nanoindentation technique is a reliable method and whether it can be used to measure the surface hardness (H) in friction stir welded aluminum alloys. In order to test the reliability of nanoindentation technique, nanohardness values for friction stir welded aluminum alloys were compared to microhardness values. Additionally, the onset of plasticity (yielding) is investigated.Design/methodology/approachNanoindentation experiments were performed for the determination of onset on plasticity (yielding) and comparison of local mechanical properties of both welded alloys. In order to test the reliability of nanoindentation technique, nanohardness values for friction stir welded AA6082 were compared to microhardness values. The specimen was tested using two different instruments – a Vickers microhardness tester and a nanoindenter tester for fine scale evaluation of H.FindingsThe results of this study indicate that nanohardness values with a Berkovich indenter reliably correlate with Vickers microhardness values. Nanoindentation technique can provide reliable results for analyzing friction stir welded aluminum alloys. The welding process definitely affects the material mechanical properties.Originality/valueMicrohardness and nanohardness obtained values can be correlated carefully, regarding the similarities and the differences of the two above mentioned techniques.